Notifications in the Google bar

When you receive a notification, the notification area in the Google bar will turn red and show the number of new notifications.
If you click the notification area in the Google bar, you’ll see a
summary of your recent notifications. When you click a notification, a
preview of the event that generated the notification will appear in the
drop-down menu. You can take action on each notification right from the
notifications menu, like commenting on a post or adding someone to a
circle. To navigate between notification previews, click Newer and Older.
To view all your notifications click View all. To
close the notifications menu, click the notification area in the Google
bar again, or click outside of the notifications menu.

You can navigate in the notifications menu using
keyboard shortcuts! When you're viewing the summary of your
notifications, use the J and K keys, or the right and left arrow keys to move between older and newer notifications when you're viewing notification details.

Games notifications

By default, notifications from Google+ games will also appear in the
Google bar. Your notifications may display as either a coalesced
collection of all new games notifications, or some games may have their
own notifications displayed.
If you'd like to not see any games notifications in the Google bar, visit the settings page and uncheck the box next to "Show Google+ games notifications in the Google bar."Pradeep Singh